Telephone exchange system



Jan. 12, 1932; L. F. PORTER TELEPHONE EXCHANGE SYSTEM Fild March 24,1930 INVf/VTOR L. E PORTER ATTORNEY Patented Jan. 12, 1932 UNHTEDs'rxerss PATENT oerics during the ringing interval.

TLESYLIE F. PORTER, F rAssAIo, NEW JERSEY, ASSIGNOR T0 BELL TELEPHONELABORA- TORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION. OF NEWYORK TELEPHONE EXCHANGE SYSTEM Application filed March 24, 1930. SerialNo. 438,253.

when the ringing key is released.

These clicks are caused by an oscillatory discharge from the line,.whichis charged Such discharges are more pronounced in the case of lineshaving lumped capacity and inductance in bridge thereto, as for example,a repeating coil winding having a condenser connected in series at itsmid-point.

A feature of the invention resides in the iprovision'of means whereby asuitable resistance is automatically connected, for a momentaryinterval, in series or bridge with the operators receiver upon releaseof the ringing key, which absorbs alarge portion of the followingdischarge. In other words,

the efliciency of the receiver circuit is decreased to'such a point thatthe discharge oscillations are not troublesome to the operator. V

The invention will be understood from the following description, whenread in connection wi h the accompanying drawing. The drawing representsan operators cord circuit arranged to prevent objectionable clicks inthe operators receiver when the operator releases the :inging keyfollowing theapplication of ringing current to a toll line shown at theright which is similar to the toll line shown in Fig. 3 of U. S. Patent1,608,524.

The cord circuit of this application is otherwise very similar to thecord circuit also shown in the above noted Patent, No. 1,608,- 524.

- It willbe assumed that the operator has relay 4, contacts 7 of key 2and the sleeve conductors of the plug 1 and the calling line L1 toground. The operating circuit for re lay may be traced from battery,lower winding of relay 5, contacts v8 of key 2, and contacts 9 of relaylO to ground. The operation of relay 5 closes at its contacts 11 acircuit for operating relay 10 which may be traced from groundedbattery, winding of relay 10, contacts 11 of relay 5 and contact-s12 ofkey 2 to ground. Relay 10 in operating closes its make-before-breakcontacts 13, thereby completing a locking circuit for relay 0 throughits upper winding. Immediately thereafter the original energizingcircuit for relay 5 is broken by the opening of contacts 9 of relay 10.The operation ofrelay 10 which is common to a plurality of cord circuitsC at the position prevents other cord circuit relays corresponding todelay 5 from operating. This feature, however, has no relation to thepresent invention and will not be discussed further.

It is further assumed that the calling line is to be extended overoutgoing toll line L1 and the operator, therefore, inserts plug 14 ofher cord circuit C- into jack if) of the line L1, thereby completing acircuit for operating relay 16 in the operators position circuit,provided the talking key 2 is still operated, which may betraced fromgrounded battery,

winding of relay 16, contacts 17 of key 2 and the sleeve conductors ofthe cord and jack to ground. The operation of relay 16 connects theoperators telephone to the called line L1 over a circuit including thecontacts of relay 16, contacts 18 and 19 of relay 5, and normal contacts20 of the ringing key BK to the tip and ring conductors of the line L1The operator may now ring on the line L1 by operating the ringing key BKto the left, which opens the t p conductor oi the cord at contacts 20 oiRK, thereby disconnecting the operatcfs telephone, and at contacts 21connects direct current in series with relay 22 to the tip conductor ofthe cord and line to operate relay 23in the toll line. Relay 23 operanil connectsringing current to the line. operates in series with relay 23and, at its contacts 27, completes a short circontacts 26 of RK andcontacts 12 of key 2 to ground. Relay 24: in operating opens'itscontacts 29 but the short circuit around resistance 28 is maintained, atthis time, over contacts 27 of relay 22. When the ringing key RK isreleased, relays 22 and 23 release.

Relay 22 which is a normally fast releasing relay immediately opens i tscontacts 27 there- ,by removing the short circuit from resistance '28 inorder that when relay 23 releases to reconnect the tip and ring of thecord to the line, the discharge of condenser 30 in the line Will bepartiallyabsorbed in the resistance 18, thereby preventing anobjectionable click in the operators receiver. Release of relay 22 opensthe circuit of relay 2twhich starts to release, but this rela which isof a sluggish character, releases slowly and there is an appreciabletime interval, before relay 24% completes its contacts 29, thatresistance 28 is in series withthe receiver 6. This time in ter al,during Which the eificiency of the operators receiver is greatly reducedby the resistance l8,'is sufficient to tide over the oscillatorydischarge from the line. When relay24l finally releases and completesits contactsr29, a short circuit is again completed around resistance28, and the receiver again restored to its normal efliciency.

What is claimed is:

"1. In a telephone system, an operators link circuit, an operators.receiver circuit connected thereto, a key associated With said linkcircuit adapted, when'operated, to connect ringing current to thecalling end of said link, and means responsive to the release ofsaid'key to momentarily decrease the efficiency of said receivercircuit.

2. In a telephone system, an operators link circuit, an operatorsreceiver circuit connected thereto, a ringingkey associated with saidlink circuit, and means automatically responsive to the actuation ofsaidkey and its subsequent release to momentarily decrease the efliciencyofsaid receiver circuit.

3. In a telephone system, an operators link circuit, an operatorsreceiver circuit connected thereto, a ringing key associated With saidlink circuit, and means responsive to the actuation of said key and itssubse- 'quent release to momentarily increase the resistance of saidreceiver circuit.

4. In a telephone system, an operators link circu1t,"an operatorsreceivercircuit connected thereto, a ringing key associated with saidlink circuit, and means responsive totheactuation of said key and itssubsecircuit associated with each of said cord circuits, and meansjointly responsive to the connection of said operators receiver circuitto one of said cord circuits,and the actuation of the respective ringingkey and its subsequent release to momentarily reduce the elliciency ofsaid receiver circuit.

6. In a telephone system, an operators cord circuit, an operatorsreceiver circuit connected thereto, a source of ringing current, meansfor connecting said ringing current to said cord circuit, and meanseffective upon the. disconnection ofsaid ringing current to momentarilydecrease the eiiiciency of said receiver circuit.

7. In a telephone system, a called line, an operators cord circuithaving a calling end connected tosaid called line,an operators receivercircuit connected to said cord circuit, a ringing key associated withsaid cord ircuit and adapted, when operated, to cause ringing current tobe applied to the called line, means associated with said receiver fordecreasing the eiiiciency thereof, said means being normally disabled,and means responsive tothe operation of said ringing key and itssubsequent release to momentarily rehigh resistance, and meansresponsive to the operation of said ringing key and its subsequentrelease to momentarily remove said short circuit from around said highresistance. V

9. In a telephone system a called line, an operators link circuit havinga calling end connected to said called line, an operators receivercircuit connected to said link circuit, a ringing key associated withsaid link circuit adapted, when operated, to cause ringing current to beapplied to said called line, a high resistance in series with saidreceiver circuit, a short circuit path around said resistance, and meansresponsive to the operation and subsequent release of said ringing keyto momentarilyopen said short circuit path; i y

In witness whereof, I hereunto subscribe my name this 20th day of March,1930. LESLIE F. PORTER.

